Desorption of halogenated organics from model solids, sediments, and soil under unsaturated conditions. 2. Kinetics

Journal Article · Sat Jan 01 04:00:00 EST 1994 · Environmental Science and Technology; (United States)

DOI:https://doi.org/10.1021/es00050a010· OSTI ID:7043140

Farrell, J; Reinhard, M ^[1]

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1. Stanford Univ., CA (United States)

The mechanisms controlling desorption rates from soils and sediments were investigated by measuring TCE desorption kinetics from model solids, sediments, and soil under unsaturated conditions at 100% relative humidity. A new experimental methodology enabled measurement of desorption rates over more than 7 orders of magnitude and revealed that intraparticle pores of molecular dimensions may be responsible for the slow release of sorbed contaminants. Desorption kinetics proceeded on two distinct time scales, and all solids had both a fast and slowly released fraction. The amount of slow desorbing TCE was found to depend on the initial vapor concentration, but not in direct proportion. At TCE vapor concentrations near saturation, the fast fraction comprised the majority of the sorbed TCE and required less than 10 min for desorption, whereas the slow desorbing fraction was released over periods of months to years. Although model solids with uniform pore and particle sizes were used, a pore diffusion model was not adequate to describe both the fast and slow desorbing fractions. The measured physical properties of the solids were not useful for making a priori predictions and, in comparisons among the solids, did not correlate with the amount and the rate of slowly released TCE. The Freundlich isotherm exponents correlated with the fraction of slowly released TCE, but isotherm nonlinearity was not sufficient to account for the dual rate behavior. 27 refs., 18 figs., 5 tabs.

• OSTI ID: 7043140
• Journal Information: Environmental Science and Technology; (United States), Journal Name: Environmental Science and Technology; (United States) Vol. 28:1; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
54 ENVIRONMENTAL SCIENCES
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
ADSORPTION
ADSORPTION ISOTHERMS
AQUIFERS
CHEMICAL REACTION KINETICS
COMPILED DATA
DATA
DESORPTION
DIFFUSION
FORECASTING
HALOGENATED ALIPHATIC HYDROCARBONS
HUMIDITY
INFORMATION
ISOTHERMS
KINETICS
LAND POLLUTION
MATHEMATICAL MODELS
MATTER
MINERALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC MATTER
PHYSICAL PROPERTIES
POLLUTANTS
POLLUTION
POROSITY
REACTION KINETICS
SEDIMENTS
SOILS
SORPTION
SURFACE PROPERTIES